1. Field of the Invention
The present invention relates to a fuel cell, and more particularly to a technology to integrate a gasket-combined frame inside a fuel cell, a separator, and a membrane electrode assembly.
2. Description of the Related Art
A fuel cell stack generally includes an anode, a cathode, and a solid polymer electrolyte membrane disposed between the anode and cathode. Fuel cells power a load with power generated by chemical reaction between an oxidant (e.g., oxygen in air) supplied to the cathode and a fuel (e.g., hydrogen) supplied to the anode.
A unit cell of a fuel cell typically has a structure in which a cathode-side separator supplied with an oxidation gas, an anode-side separator supplied with a reduction gas, and a polymer electrolyte membrane, and a gas diffusion layer are stacked together to form a fuel cell stack. The unit cells are often stacked in a vertical direction and fixed together to form such a fuel cell stack.
In particular, a separator is provided in between each of the units of the fuel cell stack in order operated the fuel cell stack effectively. These separators perform multiple functions. For example, the separator functions as a fuel-oxidant supply passage to supply the oxidant (often air) to the cathode and the fuel to (often hydrogen) the anode in the fuel cell stack. Also provided in the separator are both a coolant supply passage to cool the fuel cell stack, and a current passage to transmit electric current therethrough.
Given multi-faceted nature of the separator, it is required to have gas tight and liquid tight seal around each of the passages therein so that fuel, oxidant, and coolant cannot be mixed. In order to ensure a liquid tight and gas tight seal in between the sections of the separator, a gasket made of rubber is arranged on the surface of the separator. This gasket functions to maintain surface pressure and seal each of the passages.
FIGS. 1 and 2 illustrate a conventional unit cell 500 including separators 520, membrane electrode assemblies (MEAs) 510, and gaskets 530 disposed between the separators 520 and the MEAs 510. In order to produce this structure, an adhesive is spread on the separators 520 and then fluorine-based gaskets 530 are produced through injection molding.
A manufacturing method for the separator 520 includes (a) providing materials, (b) molding (stamping) a fluid channel, (c) performing surface treatment to form a conductive surface, and (d) performing injection molding to produce an integrated gasket. Each of these steps is sequentially performed. The integrated gasket 530 of the separator is produced in a manner that an injection gasket mold holds an edge portion of the separator 520 at a predetermined pressure and a pressurized injection molding process using a gasket material is performed on the surface of the separator 520.
When the material of the gasket leaks through a gap between the separator 520 and the mold of the gasket during the injection molding, the leaked material forms burrs in the openings/passages. In this case, a deburring process is performed to remove the burrs. However, the surface of the separator 520 is susceptible to physical damage as well during the deburring process, increasing a defect rate of the separators.
Additionally, when multiple unit cells 500 are stacked to form a fuel cell stack, a reference point for stacking is needed. The degree of alignment between the separators 520 and the degree of alignment between the separator 520 and the MEA 510 are determined based on the reference point. When misalignment between the separator 520 and the MEA 510 occurs, the gas diffusion layer (GDL) adjacent to the MEA 510 is also misaligned with respect to the separator 520. In this case, the GDL layer disposed on the separator 520 is misaligned and the GDL layer blocks passages of reaction gases, lowering distribution of the reaction gases. This results in a decrease in the performance of the unit cell 500.
The foregoing is intended merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art that is already known to those skilled in the art.